1. Field of the Disclosure
The present disclosure relates to a laser unit and an optical fiber laser.
2. Description of the Related Art
Various high-output laser units have been made into practical use in recent years. Specifically, as a particularly high power laser unit, an optical fiber laser using an optical fiber, as an amplification medium, having a core portion doped with rare-earth element draws attention, and is used for fabrication or the like of metal. In high power laser units as such, a highly intense, such as exceeding 10 W, a laser light is inputted to an optical fiber.
Herein, there is a problem that, if a highly intense laser light is inputted to an optical fiber, the optical fiber may be subjected to heating and damaging at a bending portion of the optical fiber sometimes. This is because a light propagating through the optical fiber leaks, as bending loss, at the bending portion of the optical fiber to a coated portion of the optical fiber, and the coated portion absorbing this leak light is subjected to heating, and moreover to damaging. It is considered that the heating and damaging of the optical fiber by the bending loss as such are caused by a light, among those being inputted to the optical fiber, propagating with a cladding mode coupled to a cladding portion of the optical fiber. For that reason, a technology for reducing the light propagating with the cladding mode is disclosed (for example, see Japanese Laid-open Patent Publication No. 2010-2608).
However, even if the light propagating with the cladding mode is reduced, heating and damaging may occur at the bending portion of the optical fiber sometimes.
There is a need for a laser unit and an optical fiber laser highly that are reliable and miniaturized.